Phototherapy can be shown to decrease brain damage in the infant Gunn rat without interfering with overall growth only if careful attention is paid to maintaining an abundant supply of calories and fluid. Recent work here and in Dr. Butcher's lab has demonstrated a remarkable degree of protection to the brain from a high fat diet fed either to the suckling mother or to the infant rat by tube. This appears to be independent of, but additive to, the effects of phototherapy. We believe that ample fat stores, by acting as a bilirubin trap, and ample reserves of vitamin E and beta-carotene, acting in their capacities as singlet oxygen and free radical scavengers, provide protection against the toxic effects of both bilirubin and light. These data are being pursued by in vivo and in vitro studies in the Gunn rat. Brain damage will be evaluated by a standardized Purkinge cell count of the cerebellar vermis at day 14 and psychologic testing at age 3 months. Additionally we are investigating the possibility that a temporary riboflavin deficiency, related to destruction of this photo-labile compound, is responsible for the hemolysis associated with the "bronze baby" syndrome. To this end we are assaying the activity of the flavin dependent enzyme, glutathione reductase, as well as glucose-6-phosphate dehydrogenase and reduced glutathione in rat red cells exposed in vivo and in vitro to blue fluorescent lamps.